Priority is claimed with respect to German application No. 199 16 207.7-14 filed in Germany on Apr. 10, 1999, the disclosure of which is incorporated herein by reference.
The invention generally relates to a pivot motor and particulary to the sealing of a pivot motor.
Pivot motors of the abovementioned type are known from DE 43 37 815 C1 and are provided in the tip region of their housing and shaft vanes, which delimit working chambers that follow one another in the circumferential direction, with grooves in which there are sealing elements which, as frame-shaped sealing elements, form a closed sealing boundary between the respective working chambers, in which they form a seal between the groove base and the respectively opposite peripheral boundary on the housing or shaft side and the mutually opposite end boundaries, which are at an angle to the said peripheral boundary.
In the known solution, the sealing elements each comprise a sealing frame which surrounds an inner sealing insert, this sealing insert comprising a central inner body and an elastomer ring which lies between the central inner body and the frame and by means of which the frame is loaded towards the associated sealing boundaries and by means of which the sealing element is also connected to a pressure-tight, disc-shaped unit transversely to the frame plane. Arranged in the groove together with this unit and supporting the latter in the transverse direction there is in each case a disc-shaped filler body which effects transverse stabilization of the multi-part sealing element and allows adaptation to the respective groove width.
Pressure fluid passes out of the working chamber respectively supplied with pressure medium, along the surfaces of the housing and the shaft with which the sealing element interacts, and into the respective groove and here acts on the sealing element, the pressure medium also intensifying the contact pressure acting on the sealing frame.
The construction described of the sealing element with an associated filler piece forms a relatively complicated unit which is not easy to handle during assembly.
DE 197 42 881 A1 has furthermore disclosed a pivot motor, the working spaces of which are separated from one another by vanes which are provided with radial grooves running along their length and are press-fitted into the frame-sealing elements. These sealing elements each comprise a plate-shaped insert which is provided on both sides, i.e. facing the walls of the respective groove, over its periphery with sealing rings by means of which the intended sealing is effected in the radial and axial direction.
The object on which the invention is based is to allow efficient sealing with a sealing element of simple construction.
According to the invention, use is made for this purpose of a sealing element in which the groove width is occupied by the sealing frame, which for this purpose has an encircling, inwardly open U-shaped limb cross section, with the result that loading of the frame in the direction of the groove walls and in the direction of the encircling sealing boundaries is achieved by means of the fluid pressure building up in the interior of the frame. According to the invention, this pressure build-up is made possible by the fact that the connection with the respectively pressurized working chambers opens into the frame interior, the simplest method of achieving this being in each case at least one hole passing transversely through the respective vane. In the context of the invention, a short-circuit connection is at the same time avoided by the fact that the inner sealing insert is designed as a blocking diaphragm which engages at the edge in the encircling channel of the sealing frame, with the result that pressure building up on one or other side leads to corresponding transverse loading, by means of which the diaphragm is pressed against one of the channel walls.
In this configuration in accordance with the invention of the sealing element, this sealing element comprises just two parts which can advantageously be connected by fitting the inner sealing insert into the frame and which can be installed easily. Tolerance problems are largely avoided with the solution according to the invention and it has proven particularly expedient, particularly as regards the use of the sealing element according to the invention in a pivot motor with relatively short pivoting travels, if the sealing frame is composed of an elastomer, e.g. a rubber-like material, which has a relatively high flexibility in the circumferential direction too, i.e. as regards the spacing of the limbs of the frame relative to one another, thus giving high adaptability with the capacity for good tolerance compensation. At the same time, it is also possible for a certain preload to be applied to the sealing frame by means of the inner sealing insert, and to do this both in the sealing plane and transversely to this.
In order to achieve high stability, even when using elastomeric material, and to do this with low coefficients of friction, it has proven expedient to coat this material on the outside, e.g. with proportions of PTFE applied, sprayed on or introduced into the elastomer mixture.
In order at high pressure loading to avoid high pressures on the frame walls acted upon by the inner sealing insert and bounded by the channelxe2x80x94referred to below for short as channel wallsxe2x80x94it has proven expedient to thicken the sealing insert at least in part in the area within the frame, more specifically such that the thickened portion forms a travel limiter by support against the respective groove wall.
The solution according to the invention also offers the possibility of cutting out relatively large cross-sectional areas of the groove walls as connecting paths to the working chamber respectively supplied with pressure medium, in particular pressure fluid, thus also allowing the pivot motor to be made lighter in weight in conjunction with the configuration in accordance with the invention of the sealing element.